When would I want to use a factor vs color output?
On the Noise texture node, Factor is a number from 0 to 1, whereas Color is a three number set, all of which range from 0 to 1. If you input Color into a Factor socket like the one on the Color Ramp node, it will average the three color channel numbers and turn it into greyscale. If you wanted to get three semi-related random values together, you could use the Color output and split it with the Separate RGB converter node. Or if you wanted semi-random “fluffy” color, of course, you could use it without splitting. For one Color Ramp node, however, I would just use Factor.